The Dream Monster
The monster in Ippolit’s dream that looks like a scorpion but isn’t a scorpion is a power symbol in the novel. The key to unraveling its meaning lies within the long passage in which he describes is hideous appearance: “I had been told it was poisonous, but what worried me most of all was the question who had sent it into my room.” Thus, the monstrous element is not so much what this repulsive creature is capable of doing, but who is responsible for making him fear that its capacity to harm may actually affect him. This perfectly encapsulates the fear that a more broadly abstract fear of the corruption of society around you is growing increasingly less abstract and posing more of a personal threat.
The Holbein Painting
The copy of the painting by Holbein of Christ being lowered from the Cross after the resurrection is a symbolic foreshadowing of Myshkin’s own path toward sacrifice and, on a larger thematic scale, his implication of the idiot-as-Christ figure.
Marie
The long story of the shamed woman named Marie told by Myshkin has obviously allegorical similarities to another woman with a very similar name. The jeering, spitting crowd who make great sport of humiliating Marie is deeply symbolic as it ties the characterization of the idiot to Christ through his parable of what is essentially a contemporary updating of the story of Mary Magdalene.
Epilepsy
More specifically, epileptic fits are the real symbol here. The dramatic and uncontrollable convulsions accompanying an epileptic seizure have long been assumed as the genuine medical cause behind any number of superstitious attributions. Thus epileptic fits are a symbol for how people view Myshkin. His behavior from the outside could be confusing and easily assumed to be symptomatic of idiocy while to others they represent a kind of equally superstition-based purity and innocence.
Rogozhin's House
The home of Rogozhin is like a symbolic incarnation of the man. Or, perhaps, Rogozhin is a personification of the house. Both are dark, foreboding and malevolent. The protective bars on the windows of the home are like metal projections of his own obsessive urge to control every aspect of his life, including the lives of those he allows in.
